The prior art embraces machines of the type in question, which comprise a dispensing disc rotatable intermittently about a vertical axis and furnished with a ring of cavities, each containing a quantity or portion of tobacco that will correspond to the contents of a single pouch.
The portions are released into the single cavities at a filling station by a hopper containing a supply of powdered tobacco, en masse, treated with flavouring and moisturizing agents.
Downstream of the filling station, the machine comprises skimming means that serve to remove any excess tobacco from each of the cavities.
With the disc in rotation, the cavities are carried beyond the skimming means and toward a transfer station where the single portion of tobacco contained in each cavity is ejected.
Installed at this same station are pneumatic ejection means comprising a nozzle positioned above the dispensing disc. At each pause in the movement of the disc, a portion of tobacco is forced by the nozzle from the relative cavity into a duct, of which the mouth lies beneath the disc and in alignment with the nozzle, and toward a wrapping station where the single pouches are formed.
The wrapping station comprises a tubular element, placed at the outlet of the duct and functioning as a mandrel over which to fashion a tubular envelope of paper wrapping material.
The material in question consists of a continuous web decoiled from a roll and fed in a direction parallel to the axis of the tubular element, which is wrapped progressively around the element and sealed longitudinally.
Beyond the tubular element, the machine is equipped with transverse sealing means of which the operation is synchronized with the transfer of the tobacco portions, in such a way that each successive portion will be enclosed in a relative segment of the continuous tubular envelope of wrapping material delimited by two consecutive transverse seals.
The successive tubular segments of wrapping material, formed as pouches containing respective portions of tobacco, are separated one from the next through the action of cutting means positioned downstream of the transverse sealing means.
Once separated, the individual pouches are transferred by conveyor belts of conventional type to a station where retailable packs of appropriate design are filled with a given number of the single pouches.
A sampling step is effected periodically at a given point between the cutting station and the packing station, which involves inspecting and weighing the pouches manually.
The weights of the sampled pouches are averaged, and the resulting value is compared with a range of reference values.
In the event of the averaged weight falling outside the prescribed range, part of the output is rejected and the machine will be stopped so that the settings of feed mechanisms can be readjusted to ensure the tobacco is being portioned at the correct weight.
Machines of the type described above present certain drawbacks.
First, the method of check-weighing items on a sample basis, as described above, is one that produces a high number of rejects in the event of there being a malfunction in the machine, given that where an averaged weight value falls outside a given range of values, all pouches of the sample will be discarded.
Consequently, even pouches of correct weight will be discarded as part of the rejected sample.
Moreover, it is not always possible in these machines for defects in production to be identified immediately and accurately, since measurements are derived by sampling a given number of pouches, and not by checking every single pouch produced.
The object of the present invention is to provide a machine for manufacturing single pouches of cohesionless material that will be unaffected by the drawbacks mentioned above in connection with machines of the prior art, and able thus to ensure efficiency, precision and an extremely low percentage of reject items in production.
With reference to FIG. 1, numeral 1 denotes a machine for manufacturing pouches 2 containing a cohesionless material, in particular a smokeless tobacco product.
The machine 1 comprises a hopper 3 filled with the material in question, and conveying means 4 that consist in a conveyor 5 embodied as a dispensing disc, denoted 5a, furnished with a plurality of pockets 6 fashioned as bottomless cavities 7 of circular shape, arranged around the periphery.
The dispensing disc 5a rotates intermittently and anticlockwise (as viewed in FIG. 1) about a relative axis X, between a delivery station 8 beneath the hopper 3, where each cavity 7 is filled with a predetermined portion 100 of tobacco, and a transfer station 9 at which the successive portions 100 of tobacco are ejected from the cavities 7.
The machine 1 further comprises a form-fill-and-seal wrapping station 10 where the portions 100 of tobacco removed from the conveyor at the transfer station 9 are taken up and enclosed in respective pouches 2.
Also indicated in FIG. 1 are interconnecting means 11, embodied as a rectilinear duct 12, interposed between the transfer station 9 and the wrapping station 10.
Numeral 13 denotes skimming means located downstream of the hopper 3, as referred to the direction of rotation of the disc, and serving to remove any excess tobacco from the cavity 7.
The hopper and the skimming means together constitute feed means 101 by which the cohesionless material is dispensed and portioned.
Referring to FIGS. 1 and 1a, the transfer station 9 incorporates pneumatic forcing means 14, located above the disc 5a, comprising a tubular element 15 of diameter substantially equal to the diameter of the cavities 7, aligned on a vertical axis and divided internally by radial walls 15a into four sectors 15b, which is connected uppermost to a source of compressed air (not illustrated).
The wrapping station 10 comprises a tubular mandrel 16 positioned at the outlet end of the rectilinear duct 12, around which a continuous web 17 of wrapping material is formed into tubular envelope 18.
The web of material 17 is decoiled from a roll (not illustrated) and wrapped around the tubular mandrel 16, by degrees, through the agency of suitable folding means.
The edges of the web are joined and sealed longitudinally to form the tubular envelope 18 by ultrasonic welders 19 located in close proximity to the tubular mandrel 16.
Referring to FIGS. 1 and 2, the machine 1 also comprises sealing means 20 located beneath the tubular mandrel 16, of which the function is to bond the tubular envelope 18 transversely and thus form a continuous succession 21 of pouches 2, each containing a single portion 100 of tobacco. The transverse sealing means 20 are followed downstream by a pair of transport belts 22 looped around respective pairs of pulleys 22a, serving to advance the continuous succession 21 of pouches 2 toward cutting means 23 by which the single pouches 2 of the selfsame succession 21 are divided one from the next.
As illustrated in FIG. 1, the machine further comprises a microwave emitter device 102 interposed between the paired transport belts 22 and the cutting means 23, through which the single pouches 2 of the continuous succession 21 are caused to pass, and of which the function is to sense the mass density of the tobacco particles contained in each of the pouches 2 making up the succession 21.
The microwave emitter device 102 is connected to a master control unit 103 programmed to calculate the weight of each pouch 2, on the basis of the density sensed by the emitter device, and compare the resulting value with a previously selected range of reference values.
The master control unit 103 is connected to the aforementioned tobacco feed means 101, and to an expulsion device 104 positioned to engage the pouches 2 at a point downstream of the cutting means 23.
The emitter device provides means 105 by which the weight of the pouches can be checked in line.
In operation, with the disc 5a set in rotation, the cavities 7 are directed one by one under the hopper 3 and filled with respective portions 100 of tobacco, each destined to provide the contents of one pouch 2.
Each cavity 7 then passes under the skimming means 13, which will remove any excess tobacco released from the hopper.
Thereafter, the cavities 7 advance in succession toward the transfer station 9 and are positioned under the tubular element 15.
At this point, a pneumatic selector, schematized in FIG. 1 as a block 14a, connects the four sectors 15b of the tubular element 15 sequentially to the source of compressed air in such a way that corresponding jets are directed in succession onto different areas of the portion 100 of tobacco contained in the cavity 7.
As a result, the portion 100 of tobacco is removed by degrees from the respective cavity 7 and directed gradually into the duct 12 beneath.
Forced downward by the air jets, the portion 100 of tobacco passes along the rectilinear connecting duct 12 and into the tubular mandrel 16, which is ensheathed by the web 17 of wrapping material.
The envelope 18 obtained from the web of paper material is sealed lengthwise by the ultrasonic welders 19, and crosswise, at the outlet end of the tubular mandrel 16, by the transverse sealing means 20.
The operation of the transverse sealing means 20 is intermittent, and timed to match the frequency at which successive portions 100 of tobacco are fed into the transfer station 9, in such a way that each portion 100 of tobacco will be enclosed between two successive transverse seals.
Thus, a continuous succession 21 of tobacco-filled pouches 2 will emerge, connected one to the next by way of the transverse seals.
The continuous succession 21 of pouches 2 is advanced by the transport belts 22 toward the microwave emitter device 102, which detects the mass density of each pouch 2 and sends a corresponding signal to the master control unit 103, which in turn will calculate the weight of the single pouch 2 from the mass density measurement.
In the event that the detected weight of a pouch 2 should be out of range, the master control unit 103 sends a first signal to the expulsion device 104, which will remove the pouch 2 in question from the production line.
The control unit 103 also forms part of a feedback loop with the tobacco feed means 101, to which it is linked in such a way that defects in the weight of the pouches 2 can be corrected.
At a given point downstream of the emitter device 102, the single pouches 2 are separated one from the next by the cutting means 23.
In the embodiment of FIG. 2, the pockets of the dispensing disc 5a are fashioned as elongated slots 24 and the forcing means consist in a single pneumatic nozzle 25 positioned at the transfer station 9.
In this instance, the portions 100 of tobacco are transferred from the slots 24 to the duct 12 with the disc 5a in rotation, as each single slot 24 passes beneath the nozzle 25.
Likewise in this solution, the transfer of the portions 100 of tobacco into the rectilinear duct 12 occurs gradually.
In a further embodiment (see FIG. 3), the conveying means 4 appear as a drum 26 rotatable intermittently and anticlockwise, as viewed in the drawing, about a horizontal axis A. The drum 26 is interposed between a bottom end of the hopper 3, delimited by two side walls 3a and 3b, and the transfer station 9.
The drum 26 presents a cylindrical wall 27 with a band 28 of predetermined width rendered permeable to air by a plurality of through holes 28a. 
The enclosure 29 delimited by the cylindrical wall 27 is divided by two radial walls 29a and 29b into two sectors, denoted 30 and 31.
A first sector 30, located adjacent to the outlet of the hopper 3 and extending around to the transfer station 9, is connected by way of a duct 30a to a source of negative pressure (not illustrated).
The remaining sector 31, positioned adjacent to and above the transfer station 9, is angularly complementary to the first sector 30 and connected by way of a further duct 31a to a source of compressed air (not illustrated).
In operation, with the drum 26 set in rotation and exposed to the aspirating action of the negative pressure source, the air-permeable band 28 will gradually collect a continuous stream 32 of tobacco, which is kept at a prescribed and constant thickness through the action of a levelling roller 33 rotating similarly anticlockwise about an axis B parallel to the axis A aforementioned, internally of the hopper 3 and adjacent to one side wall 3a. 
The continuous stream 32 advances between two side panels 34 extending concentrically with the drum 26 as far as the transfer station 9, where a given length of the stream 32, corresponding in quantity to one portion 100, will be detached gradually from the drum by a jet of compressed air forced through the holes 28a of the air-permeable band 28, and directed into the duct 12 in the manner described previously with reference to other embodiments.
It will be seen that the forcing means 14, which are pneumatic in the various embodiments described thus far, might also be of mechanical design.
In an alternative embodiment of the machine, not illustrated, the forcing means might be embodied as a mechanical plunger invested with reciprocating motion and insertable through the cavities of the dispensing disc when positioned at the transfer station.
The microwave emitter device 102 might also be substituted by a gamma ray device or a beta ray device.
The elements of the design as described above are readily applicable to a twin track type of machine.
In this instance, the conveying means will consist either in a disc with two rings of cavities, or a drum with two air-permeable bands, in such a way that two portions of tobacco can be supplied simultaneously to the transfer station, and each then directed into a respective duct.
Self-evidently, adopting the machine according to the present invention, the aforementioned drawbacks connected with the prior art can be overcome, inasmuch as a weight check is conducted on every single pouch produced, rather than on predetermined samples only.
With the present invention, moreover, it becomes possible to reject only those pouches of which the weight registers outside the predetermined range of reference values, since the weight check is conducted on each single pouch rather than using an average value calculated on a relatively large number of pouches.
Finally, by connecting the control unit and the tobacco feed means as part of a feedback loop, any defects in production can be corrected automatically and in-line, without having to interrupt the operation of the machine